1. Field of the Invention
The present invention relates to an organic EL device, and more particularly to a light source used for near field optics.
2. Description of the Related Art
Nowadays, for the purpose of write and read of a high density optical disk exceeding analysis limitation of light, attention is being given of an optical technique using the near field optics. The near field optics is to irradiate an object for read with light in a state where a light source is made sufficiently close to the object from an opening having a diameter much smaller than the wavelength of the irradiated light so that changes in optical property smaller than the wavelength of irradiated light can be read.
The light source used in a near field optical recording system using the near field optics must satisfy the conditions that its opening can be micro-machined, and it can approach the object. In order to satisfy these conditions, as shown in FIG. 15, a probe 61 has been proposed which: is formed by etching an optical fiber by an etching solution having a specific composition. By placing the probe 61 at a close position (100-200 A) from an object 63 so that a region irradiated with light is limited to a an minute area, write and read of the optical property smaller than the wavelength of light can be made.
However, the above etching technique used to form the probe requires a very sophisticated technique. In addition, the probe, which has a protrusion, is low in mechanical strength.
Therefore, the light source used in the near field optical recording system could not be realized easily and surely. The present invention intends to solve such a problem.
An object of the present invention is to provide a simple light source which can be used for near field optics.
A first aspect of the device is a minuscule light-emitting device having a light source used for near field optics, said light source being an organic EL device comprising:a lower electrode;
an organic EL layer placed on or above the lower lectrode; and an upper electrode placed on or above said organic EL layer, whereby an object for read is irradiated with light in a state where the light source is made sufficiently close to the object, from an opening having a diameter with a maximum length much smaller than the.wavelength of the irradiated light so that changes in optical property of the object are read.
Therefore, by micromachining the superposed area so that the light emitting region has a minimum width that is smaller than the light emitting wavelength of the organic EL device, the organic EL device can be easily used for a light source in the near field optics.
A second aspect of the device is a minuscule light-emitting device as set forth in the first aspect, wherein said lower electrode and said upper electrode are orthogonal to each other.
Preferably, the lower electrode and the upper electrode are orthogonal to each other. Therefore, the above superposed area can be easily formed. A third aspect of the device is a minuscule light-emitting device as set forth in the first aspect, wherein in a region where said lower electrode and said upper electrode cross, at least one of said lower electrode and said upper electrode has a portion having a smaller width than the remaining portion.
In accordance with such a configuration, since the light emitting region is defined by the region having a small width, a fine light emitting region can be easily defined.
A fourth aspect of the device is a minuscule light-emitting device as set forth in the first aspect, wherein in said organic EL device, said lower electrode and said upper electrode are formed in stripe patterns which are orthogonal to each other, and in a region where said lower electrode and said upper electrode cross, an interface between said organic EL layer and at least one of said lower electrode and said upper electrode is selectively oxidized except a portion thereof.
In accordance with such a configuration, in a region where the upper electrode and lower electrode cross, the oxidized area of the interface with the organic EL layer is an insulating area to which no electric field is applied and serves as an non-light-emitting region. Therefore, a fine light emitting area over the limit of lithography can be easily formed. By performing the oxidation through pattern exposure using a near field, a finer light emitting area can be formed.
A fifth aspect of the device is a minuscule light-emitting device as set for the in the fourth aspect, wherein said region has a minimum width which is shorter than a wavelength of light emitted from said organic EL layer.
A sixth aspect of the device is a minuscule light-emitting device as set for the in the first aspect, wherein in said organic EL device, said lower electrode and upper electrode are formed in stripe patterns which are orthogonal to each other, and in a region where said lower electrode and said upper electrode cross, said upper electrode is formed in a stripe pattern having an inverted trapezoidal sectional shape.
In accordance with such a configuration, since the upper electrode has an inverted trapezoidal sectional shape, through detouring of etching, a fine light emitting area over the limit of lithography can be easily formed.
A seventh aspect is a minuscule light-emitting device as set for the the seventh aspect, wherein in said organic EL device, said lower electrode and said upper electrode are formed in stripe patterns which are orthogonal to each other, and in a region where said lower electrode and said upper electrode cross, said lower electrode is formed in a stripe pattern having an inverted trapezoidal sectional shape in which a region exclusive of an apex is covered with an insulating film.
In accordance with such a configuration, since the lower electrode is formed in a pattern having an inverted trapezoidal sectional shape in which a region exclusive of an apex is covered with an insulating film, through detouring of etching, a fine light emitting area over the limit of lithography can be easily formed.
An eighth aspect is a minuscule light-emitting device as set forth the first aspect, wherein said organic EL device comprises: a lower electrode; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein a wavelength of light emitted from said organic EL layer is longer than that of a short side of a light emitting region.
In accordance with such a configuration, the light emitting area can be formed in e.g. a slit shape having a very smaller width so as to provide a stable minuscule light-emitting device.
A ninth aspect of the device is a minuscule light-emitting device as set for the in the first aspect, wherein said organic EL device comprises: an lower electrode; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein said upper electrode is made from a light shielding conductive film, and in a region where said lower electrode and upper electrode cross, said conductive film has a through-hole having a diameter which is smaller than a wavelength of light emitted form said organic EL layer.
In accordance with such a configuration, only the portion of the through-hole defines a light take-out area, i.e. the light emitting area of the organic EL device so that the fine light emitting area defined by only the through-hole can be obtained. In this configuration, light with enhanced intensity can be taken out.
A tenth aspect is a minuscule light-emitting device as set forth in claim 1, wherein said organic EL device comprises:a lower electrode formed on a substrate; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein said upper electrode is made from an insulating light shielding conductive film which covers the entire surface of said substrate including said upper electrode, and in a region where said lower electrode and upper electrode cross, said light shielding film has a though-hole having a diameter which is smaller than a wavelength of light emitted form said organic EL layer.
In accordance with such a configuration, only the portion of the through-hole formed in the insulating, light shielding film defines a light take-out area, i.e. the light emitting area of the organic EL device so that the fine light emitting area defined by only the through-hole can be obtained. In this configuration, light with enhanced intensity can be taken out.
An eleventh aspect of the device is a minuscule light-emitting device as set forth the tenth aspect, wherein said through-hole has a diameter which is larger on the side of said upper electrode than on the side of the surface.
In this configuration, a beam can be formed which is converged with a smaller diameter than the opening diameter of the through-hole, thereby providing finer light emission.
A twelfth aspect of the device is a minuscule light-emitting device as set forth the tenth aspect, wherein said through-hole is a slit whose width is larger on the side of the upper electrode than the side of the surface.
In this configuration, a beam can be formed which is converged with a smaller diameter than the opening diameter of the slit, thereby providing finer light emission.
A thirteenth aspect of the device is a minuscule light-emitting device as set forth the tenth aspect, wherein said through-hole is formed by beam exposure using near field optics.
In accordance with such a configuration, a finer through-hole can be formed so as to fine light emission.
A fourteenth aspect of the device is a minuscule light-emitting device having a light source used for near field optics, said light source being an organic EL device comprising:a first electrode and a second electrode having acute edges formed on a substrate so as to be opposite to each other through a fine gap; and an organic EL layer filled in said gap, whereby an object for read is irradiated with light in a state where the light source is made sufficiently close to the object, the light having a diameter with a maximum length much smaller than the wavelength of the irradiated light so that changes in optical property of the object are read.
In such a configuration, a very fine gap can be formed. The organic EL layer in the very fine gap is caused to emit light so that the reliable fine light emitting beam can be obtained.
A fifteenth aspect of the device is a minuscule light-emitting device as set forth the first aspect, wherein said organic EL device comprises:an lower electrode formed on a substrate; a light emitting layer formed on said lower electrode; and an upper electrode formed on said light-emitting layer and made of an oxygen permeable material, and wherein a partial region of the light emitting layer constitutes an oxide layer which is selectively formed by optical selective oxidation using light and oxygen which reaches through the upper electrode, and the region of the light emitting layer where the oxide layer is located serves as a non-light emitting region so that the minimum width of the light emitting region in the organic EL layer is shorter than the wavelength of the light emitted from the organic EL layer.
A sixteenth aspect of the device is an organic EL device comprising: a lower electrode; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein a light emitting region has a maximum length that is shorter than a wavelength of light emitted form said organic EL layer.
A seventeenth aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said lower electrode and said upper electrode are orthogonal to each other.
An eighteenth aspect of the device is an organic EL device, comprising: a lower electrode; an organic EL layer placed on or above the lower electrode; and an upper electrode placed on or above said organic EL layer, wherein in a region where said lower electrode and said upper electrode cross, at least one of said a lower electrode and said upper electrode has a portion having a smaller width than the remaining portion.
A ninteenth aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said lower electrode and said upper electrode are formed in stripe patterns which are orthogonal to each other, and in a region where said lower electrode and said upper electrode cross, an interface between said organic EL layer and at least one of said lower electrode and said upper electrode is selectively oxidized except a portion thereof.
A twentieth aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said region has a minimum width which is shorter than a wavelength of light emitted from said organic EL layer.
A twenty first aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said lower electrode and upper electrode are formed in stripe patterns which are orthogonal to each other, and in a region where said lower electrode and said upper electrode cross, said upper electrode is formed in a stripe pattern having an inverted trapezoidal sectional shape.
A twenty second aspect of the device is an organic EL device as set forth the sixteenth aspect,wherein said lower electrode and said upper electrode are formed in stripe patterns which are orthogonal to each other, and in a region where said lower electrode and said upper electrode cross, said lower electrode is formed in a stripe pattern having an inverted trapezoidal sectional shape in which a region exclusive of an apex is covered with an insulating film.
A twenty third aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said organic EL device comprises:a lower electrode; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein a wavelength of light emitted from said organic EL layer is longer than that of a short side of a light emitting region.
A twenty forth aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said organic EL device comprises:a lower electrode; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein said upper electrode is made from a light shielding conductive film, and in a region where said lower electrode and upper electrode cross, said conductive film has a through-hole having a diameter which is smaller than a wavelength of light emitted form said organic EL layer.
A twenty fifth aspect of the device is an organic EL device which comprises:a lower electrode formed on a substrate; an organic EL layer placed on or above said lower electrode; and an upper electrode placed on or above said organic EL layer, wherein said upper electrode is made from an insulating light shielding conductive film which covers the entire surface of said substrate including said upper electrode, and in a region where said lower electrode and upper electrode cross, said light shielding film has a though-hole having a diameter which is smaller than a wavelength of light emitted form said organic EL layer.
A twenty sixth aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said through-hole has a diameter which is larger on the side of said upper electrode than on the side of the surface.
A twenty seventh aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said through-hole is a slit whose width is larger on the side of the upper electrode than the side of the surface.
A twenty eighth aspect of the device is an organic EL device as set forth the sixteenth aspect, wherein said through-hole is formed by beam exposure using near field optics.
A twenty ninth aspect of the device is an organic EL device comprising: a first electrode and a second electrode having acute edges formed on a substrate so as to be opposite to each other through a fine gap; and an organic EL layer filled in said gap.
A thirteenth aspect of the device is an organic EL device, comprising: a lower electrode formed on a substrate; a light emitting layer formed on said lower electrode; and an upper electrode formed on said light-emitting layer and made of an oxygen permeable material, and wherein a partial region of the light emitting layer constitutes an oxide layer which is selectively formed by optical selective oxidation using light and oxygen which reaches through the upper electrode, and the region of the light emitting layer where the oxide layer is located serves as a non-light emitting region so that the minimum width of the light emitting region in the organic EL layer is shorter than the wavelength of the light emitted from the organic EL layer.
Incidentally, the expression xe2x80x9cplaced on or abovexe2x80x9d means that the upper layer is formed directly or through any other layer on the lower layer and any other layer may be formed therebetween.